Small internal combustion engines comprise a magneto for generating the impulse which triggers the ignition in those cylinders in which compression of the fuel/air mixture has occurred. In early design of such engines, the electrical pulse generated by the magneto, i.e. the magnet/coil assembly which was relatively rotated by the shaft of the engine, fired the spark plugs in appropriate order with a pulse which was increased by the action of breaker points and a voltage multiplying coil and with firing control by mechanical factors such as the offsetting of the various parts of the ignition system with respect to one another. The "advance of the spark required for increased speeds was effected by mechanically moving an element of the firing system.
These systems eliminate the need for a battery or other source of electrical energy and hence use of magneto engines has found widespread application, namely for small engines with outputs below, say, 100 hp and in a wide variety of sizes and uses.
In recent years efforts have been made to develop electronic ignition systems utilizing magneto input and, especially, electronic switching to eliminate the breaker points which have created reliability problems in the past, especially for military and government applications where the engines must conform to extremely rigid performance specifications.
While such electronic ignition systems have been developed in the past, they, too, are generally not very reliable and it is not uncommon, upon the purchase of a large number of self-contained electronic ignition control systems, even when they are purported to comply with government and military specifications, that a substantial proportion do not perform up to these standards, are inoperative, and require replacement. Customarily a magneto-type triggering is provided in addition to a magneto-type supply of the spark-firing current.